Dry process of manufacturing pressboard



Dec. 21, 1954 B. A. GORDON DRY PROCESS OF MANUFACTURING PRESSBOARD Filed March 14, 1950 2 Sheets-Sheet a :Mg

Dec. 21, 1954 B. A. GORDON DRY PROCESS OF MANUFACTURING PRESSBOARD 2 Sheets-Sheet 2.

Filed March 14, 1950 www! NNI

IN V EN TOR.

United States Patent Office DRY PROCESS OF MANUFACTURING PRESSBOARD Bruce A. Gordon, Chicago, lll.- Application li/iarchv 14,1950, Serial No. 149,485 s Claims. (Ci. 18,-415) This invention relates generally to the manufacture of sheet lumber or` pressboard, and more particularly to a continuous process for the manufacture of such material.

Wood waste materials such as sawdust, chips, shavings, and the like, have been ground, mixed with a binding material, pressed and heated to Aform sheet lumber or pressboard heretofore. It has been the practice to make such lumber or pressboard by `a batch process. cally, a given quantityof wood waste and binding have been mixed 'and placed in a press where the mixture has been subjected to heat and pressure to produce a compact lumber or boardl possessed of many desirable qualities, such` 'as resistance to moisture and varying degrees of density from very low to very high, and varying degrees of hardness, `depending upon the temperature and pressure'einployed in the process.

Production of individual slabs of lumber or board in presses as taught by the prior art has been limited and considerable ,manual laborrhas been entailed, the two combining to' produce a relatively expensive tem.

An object of this invention is the provision of a continuous` process for the manufacture of sheet lumber or pressboard.v

A more specific object of Vthis invention is the provision of a mefthoduof mixing ground wood waste and binder and progressively heating and compressing the mixture to produce sheet lumber or pressboard.

A furtherspecific objectI of this invention is the provisionof a continuousprocess of heating groundwood wastejto reduce the moisture content and to soften the lignin therein by high'frequency heating, mixing the wood waste with a4 binder, and further heating themixture byV high` frequency electrical currents while subjecting it to progressively increasing pressures to produce sheet lumber or pressboard-` n Yet another object of this invention is the provision of a continuous process of heating wood waste by high frequency electrical oscillations, grinding the waste to reduceitfto libre, further heating by high frequency oscillations the waste to a predetermined moisture content, mixing it with a binder, and applying progressively increasing pressurekwhile concurrently heating by high frequency electricaly oscillations.

By ypracticing the methods herein disclosed, I have found that it is possible to triple the rate of production of sheet lumber or pressboard from wood waste materials for a processing installation of given size. The manual labor required has been reduced by my methods from twovand one-half man hours per ton to one-half a man hour per ton of finished pressboard. Although I have heretofore referred specifically to sheet lumber or pressboard made of wood waste materials, and will continue to speak of these products by way of example, it is to be understood that my process is applicable to the produci tion of any resin board and can be used in the plastics field.

One specic embodiment of means for carrying out my inventionl is shown inthe drawings, wherein:`

with equalfacility Figure l is aside elevation vwitha portion olset ver-n Figure 2 is a top Figure l.

The drawingslarelargely diagrammatic Aand certain plan view of the structure shown in Specifi- H parts. hav

clearly.` Byufvay` of example, the; apparatus has been... Figurel. to provide a continuousside View ,and ther last working stations have been, omitted..

straightened out` in from. the lView.

Referring to thedrawings in particularity, a chip receiveror supply .bin .4 is positioned abovela weighing-- 6. The weighingconveyor includes a` pair of belt `10. A of the upper.. control the speed of the-mecha-4 conveyor rollers 8 over which is passed `an endless balance plate 12 bears against the underside reach of the belt l0 to nism (notshown) driving one of the rollers or wheels 8.

A weight 14 ycounterbalances themforceon the pressure-V 4wood waste 16 comprising -chips,

plate 12caused by shavings, sawdust and thelike, to maintain a predetermined thickness of i Il@ by varying the required. An ,elevating conveyor lfunderlies the conveyor 6 at the discharge end thereof `and is provided .Withf a spreader or battle plate 26 to maintain the proper depth or thickness of wood waste trode plates 22 are positioned directly above the wood waste i6 on the conveyor .18 land are energized from a high frequency oscillator 24 to dry the-waste 16 on the conveyor 18 -to a predetermined moisture content, and to softeny the lignin therein. The high frequency oscillator 24 is preferably of the type having the positive terminal of the power supply grounded to preclude the possibility the yWood waste` .i6 is; groundedl into wood fibers 34 which are discharged through a conduit 316 o nto a second elevatmg conveyor 38. Electrode plates ,49 similar to the` plates 22 are spaced abovethe fibers 34 and are energized from a high frequency oscillator lator 24 to dry the bers to a final predetermined moisture content.

The upper end of the elevating conveyor 38 is disposed,

directly above a hopper 44 which receives bers therefrom. A binder supply bin 46 is also positioned abovev 48 thereto at acontrolledI the hopper 44 to supply binder rate. The binder may be of processed lignin, resin or any other suitable wood binder or glue.

restricted to any particulary type. The hopper 44 leadsv directly into a mixer 50 which may comprise a plurality of mixing units driven through shaft or shafts 52 from .a motor 54. The mixer 50 empties through aconduit 56 to a vblower k56 powered by a motor 60. Conduit 62 leads from the blower 58 `to a the mixed liber and' binder 66 is accumulated in loose or fluffed condition. Discharge conduits 68 deliver `the fluffed mixture 66 from the collectorr 64 by gravity onto a linal conveyor 70 comprising an endless belt 72 stretched over an idlerfwheel or roller 74 and a driven wheel or roller '76.

The belt 72 b ductive materia A table 78 underlies a part of the belt to provide support .therefor and is provided with vertically extending structure 80 which may be flanges or endless belts to confine the ilufed fiber and binder mixture66 on the conveyor belt 72 as it is deposited through the conduits 68. Rubber pressure rolls 81 having an endless belt S2 passed over them and driven by a power source which is not shown compress the liuied mixture slightly on the vbelt 7S.l Trimming brushes S4 reduce the thickness of the uted mixture to a predetermined thickness and smooth off the top surface. As a specific example of dimensions, for a finished pressboard of 3%: inch thickness, the layer of iluffed mixture deposited on the belt 72 is about 18 inches thick. This is reduced to abouty 9*,inches by the rollers 80 and to 8V; inchesrby Patented Dec., 21, 1,954Y

e. been shiftedrslightly-.to show them..more..

waste on the upper reach of the belt i speed of thedriving mechanism as on the conveyor 18. Elec-y 42 similiarlto the oscil- Such binders are well-known in the prior art,` and I do not Wish to be cyclone collector 64 where..

is made of steel or other suitable con.

the trimming brushes 84. Prior to receiving the uffed mixture, the belt is cleaned by a belt cleaner 86 bearing against the lower reach of the belt and is greased by a belt greaser 88 to prevent the finished pressboard from adhering to the belt.

After leaving the table 78, the belt 72 is supported by a iirst caterpillar unit 90 comprising a caterpillar chain 92 passed over sprocket wheels 94. A high pressure caterpillar unit 96 is positioned above the belt 72 and first caterpillar unit 9u and inclined relatively thereto to apply progressively increasing pressure on the fiber and binder mixer 66. The high pressure caterpillar unit 96 comprises a caterpillar chain 98 passed over rollers 100. Hydraulic cylinders 102 are provided with pistons 104 which may be provided with rollers at their top surfaces if so desired. The pistons 104 press upwardly against the caterpillar chain 92 while cooperating structures 106 from the cylinders 102 extend upwardlyand overlie the caterpillar chain 98 so that progressively increasing pressure of any desired degree may be applied to the mixture 66. By way of example the pressure applied may be up to 8O pounds per square inch and the mixture after leaving the caterpillar units may spring back to a thickness of about 3 inches.

After leaving the caterpillar units 90, 96 the belt 72 is supported from below by a lower caterpillar unit 108 comprising a caterpillar chain 110 passed over the sprocket or wheel 76 carrying the conveyor belt 72 and over a sprocket 112. The sprocket or wheel 76 is driven by a motorr 114 which thus supplies power for the conveyor belt 72, the caterpillar unit 108, and the caterpillar units 90 and 96 through suitable linkage. The caterpillar chain 110 is supported intermediate the sprockets 76 and 112 by grounded steel pressure rollers 116. A heating caterpillar unit 118 is positioned above the belt 72 and above the lower caterpillar unit 108 further to compress the mixture 66 and to concurrently heat the mixture. The heating caterpillar unit 118 comprises a wire mesh belt 120 passed over pulley wheels or sprockets 122 one of which may be powered from the motor 114 by suitable linkage. Rubber covered rollers 124 appear above the upper surface of the lower reach of the wire mesh belt 120 to provide pressure upon the mixture 66. These rollers may be adjustably positioned if desired so that the pressure may be varied according to the requirements of the finished pressboard. A brush 126 slidingly contacts the wire mesh belt 120 and is v connected with one terminal of a high frequency oscillator 128 similar to the oscillator 24 and 42 previously nientioned. The other terminal of the oscillator, preferably the positive terminal, to preclude the possibility of shock, should the coupling means become shorted out, is grounded. A high frequency field is thus established between the wire mesh belt 120 and the steel belt 72 which is grounded through the caterpillar chain the grounded steel rollers 116 so that the mixture 66 is continuously heated as progressively increasing pressure is applied to it to produce a finished pressboard 130 which, in accordance with the specific examples given heretofore, may be of 3A inch thickness.

The finished pressboard is of great strength and rigidity and need not be supported for a time. Spaced from the caterpillar units 108 and 118 is a traveling cutoff saw 132 of conventional construction for traveling longitudinally with the pressboard 130 and transversely thereto to cut off the board to suitable length. A conveyor 134 is provided directly below the saw 132 to support the cut off lengths 136 of pressboard. As shown in Fig. 2 the cut olf lengths 136 are then transported sidewise by a suitable conveyor and then parallel to but in the opposite direction of their original path where they are encountered by edge trimming saws 138 which trim the edges of the pressboard to form smooth edges thereon. After passing the edge trimming saws 138 the cut olf sections or slabs 136 of pressboard are acted upon by a planer or sander 140 to provide a smooth finished surface on the pressboard. Upon leaving the planer or sander 140 the slabs of pressboard may be transported transversely as at 142 to be stacked for transportation or s torage or may be moved straight ahead to encounter a rip saw 144 which slits the pressboard slabs longi tudinally to provide narrower slabs. These slabs are then conveyed transversely as at 146 for storage or transportation.

The process 110 and o.

disclosed herein greatly-speedsV` up thel production of pressboard and the like and reduces the cost of manufacture greatly over the batch process here- Y invention is believed to lie principally in the continuous process disclosed.

Although a process has been described for the coni tinuous manufacture of sheet lumber or pressboard it has equal applicability to the production of any resin board or to the production of sheet plastics.

Accordingly, l do not wish to be limited to the specic disclosure herein but intend my invention to include all that which fairly falls Within the spirit and scope of the appended claims.

I claim:

l. The continuous method of manufacturing pressboard and the like which comprises continuously advancing woody material at a predetermined uniform rate, heating said woody material with high frequency electrical oscillations to soften the lignin in said material, grinding the heated material to reduce it to a liber, continuously advancing the resulting ber, heating said fiber while it is being advanced with high frequency electrical oscillations to reduce it to a predetermined moisture content, mixing the heated fiber with a binder therefor, blowing the resulting mixture to a collection area through air conduit means to eifect substantial iiuffing thereof, advancing the fluffed mixture so formed as a continuous mass, applying progressively increasing pressure to said mixture as it is advanced, and heating said mixture with high frequency electrical oscillations concurrently with at least a part of the application of pressure.

2. The continuous method of manufacturing pressboard and the like which comprises continuously advancing woody material at a predetermined uniform rate, heating said woody material with high frequency electrical oscillations to soften the lignin in said woody material, grinding the heated woody material to reduce it to a fiber, continuously advancing the resulting ber, heating said fiber while it is being advanced with high frequency electrical oscillations to reduce it to a predetermined moisture content, mixing the heated fiber with binder therefor, blowing the resulting mixture through air conduit means to effect the flufng thereof, advancing the fluifed mixture so formed as a continuous mass, increasing the density of the fluffed mixture, applying increasing pressure tosaid mixture as it is advanced to compact the` mixture, releasing the pressure on the mixture for a short interval of its continuous advance, applying further increasing pressure to said mixture as it is advanced, and heating said mixture substantially throughout the last mentioned application of pressure.

3. The continuous dry process of manufacturing pressboard and the like, which consists in continuously advancing woody material at a predetermined rate, heating the woody material while being continuously advanced with high frequency electrical oscillations to soften the lignin therein and to reduce the moisture content thereof, grinding the heated woody material irnmediately after the aforesaid heating thereof to reduce it to a fiber, continuously advancing the ground fiber as it is continuously received from the aforesaid grinding thereof, heating the ground fiber with high frequency oscillations to reduce it to a predetermined moisture content as it is being continuously advanced, mixing the heated fiber with a binder immediately after the aforesaid heating thereof, blowing the resulting mixture through airy conduit means to effect substantially uniform` iiuing thereof, continuously collecting and adv ancing the uffed mixture as a continuous mass, relatively lightly pressirig the mass as it is continuously advanced to increase the density thereof, applying by extended continuous surface contact on the mass progress'ively increasing pressure thereon as the mass is continuously advanced to compact the same, immediately releasing the aforesaid pressure on the mass for a short length of travel during the continuous advance thereof,

applying further increased pressure to the mass at the end of its travel under released pressure and while the mass is continuously advanced, and heating the mass substantially throughout its travel under the final application of increased pressure.

(References on following page) References Cited in the le of this patent Number UNITED STATES PATENTS Name Date Millington Jan. 7, 1930 Libberton Feb. 12, 1935 Schmidt Sept. 20, 1938 Brown Feb. 4, 1941 Crandell June 30, 1942 Elmendorf June 5, 1945 Burrell July 10, 1945 Russell Dec. 23, 1947 Roman Aug. 3, 1948 Number Number Name Date Goss Sept. 6, 1949 Heritage Mar. 6, 1951 FOREIGN PATENTS Country Date Great Britain Mar. 14, 1944 OTHER REFERENCES l0 Modern Plastic, Continuous Structural Board From Sawdust, September 1947, pages 89-91.

Modern Plastics, Resins Bond Wood Waste Board, February 1949, pages 59-62. 

